Final answer:
Desipramine is not considered a tertiary amine among the tricyclic antidepressants listed, as it is a secondary amine with two alkyl groups attached to its nitrogen atom.
Step-by-step explanation:
Among the tricyclic antidepressants listed, Desipramine is not considered a tertiary amine. The primary, secondary, and tertiary classification of amines is based on the number of alkyl groups attached to the nitrogen atom. Tertiary amines have three alkyl groups attached. In contrast, Desipramine is a secondary amine, which means it has two alkyl groups attached to the nitrogen atom, making it different from the tertiary amines like Imipramine, Amitriptyline, Clomipramine, and Trimipramine. It is also important to note that these medications are not typically prescribed on an 'as-needed' basis due to the time it takes for the antidepressant effects to manifest in patients with depression.